The subject invention relates to roof system components and a roof system that utilizes those components. More specifically, the subject invention relates to waterproof self-adhering base sheet roof system components and a roof system that includes at least one inner layer of the waterproof self-adhering base sheets self-adhered by watertight bonds to underlying and overlying layers of the roof system. Preferably, the roof system components also include waterproof fire-retardant cap sheets and the roof system includes a layer of those cap sheets that are adhered to an underlying layer of the self-adhering base sheets by the self-adhering base sheets.
Current self-adhered modified bitumen roof systems typically include an uppermost layer of cap sheets and one or more underlying roof system layers. The underlying roof system layer or layers may be: one or more base sheet layers and a roof deck; one or more base sheet layers, one or more insulation layers, and a roof deck; one or more insulation layers and a roof deck; or a roof deck.
These current self-adhered roof systems include granule surfaced and smooth surfaced cap sheets that form the topmost layer of the roof systems. One type of current cap sheet includes a reinforcement substrate, such as a fiberglass mat, polyester fiber mat, or a fiberglass/polyester fiber mat, which is encapsulated within top and bottom layers of modified bitumen. The modified bitumen is modified to make the bitumen a self-adhering material. Another type of current cap sheet includes a reinforcement substrate, such as a fiberglass mat, polyester fiber mat, or a fiberglass/polyester fiber mat, which is encapsulated within top and bottom layers of conventionally modified bitumen that is not a self-adhering material. The bottom major surfaces of such cap sheets are coated with self-adhering materials. The self-adhering modified bitumen or the coatings of other self-adhering materials on the bottom major surfaces of these cap sheets are used to self-adhere the cap sheets to underlying roof system layers.
Where the current self-adhered roof systems include one or more inner base sheet layers, the base sheets forming those inner layers include reinforcement substrates, such as a fiberglass mat, polyester fiber mat, or a fiberglass/polyester fiber mat, which are encapsulated within top and bottom layers of modified bitumen that is modified to make the bitumen a self-adhering material. The bottom major surfaces of these base sheets are self-adhering surfaces that are used to bond the base sheets to underlying roof system layers. However, the top major surfaces of these base sheets are surfaced with non-adhering materials, such as but not limited to talc, sand, or polymeric film, which remain on the base sheets after installation so that the top major surfaces of these base sheets are not self-adhering surfaces.
The modification of bitumen to make the bitumen a self-adhering bitumen rather than a conventionally modified bitumen requires: the addition of polymers to the bitumen that are other than the polymers normally used to make a conventional modified bitumen; the addition of conventional polymers to the bitumen in concentrations very different from those normally used to make a conventional modified bitumen; and/or the addition of other vehicles and modifiers to render the bitumen softer and more tacky at application and service temperatures ranging from about 40° F. to about 120° F. Thus, when compared to the conventional Styrene-Butadiene-Styrene (SBS) or Amorphous Polypropylene (APP) modified bitumen of conventional cap and base sheets, the modified self-adhering bitumen used in these cap and base sheets are softer and less resistant to flow (less viscous) when heated or subjected to compressive forces.
When tested in accordance with ASTM Test Designation E 108-00, approved Jan. 10, 2000, published April 2000, and entitled Standard Test Methods for Fire Tests of Roof Coverings (hereinafter “ASTM Test E 108”), roof systems made with conventional cap and base sheets typically meet the requirements of Factory Mutual for a Class A rated roof system. When tested in accordance with Underwriters Labortories, Inc. test designation UL 790 (hereinafter “UL Test 790”), roof systems made with conventional cap and base sheets typically meet the requirements of Underwriters Laboratories, Inc. for a Class A rated roof system. However, when tested in accordance with ASTM Test E 108 by Factory Mutual or in accordance with UL Test 790 by Underwriters Laboratories, Inc., roof systems made with cap and base sheets utilizing the softer, less viscous, self-adhering bitumen are less fire resistant than the roof systems made with conventional cap and base sheets and typically do not achieve a Class A rating.
In addition to being less fire resistant than roof systems made with conventional cap and base sheets, current self-adhered roof systems present another problem. The surfacing of the top major surfaces of the base sheets (inner ply sheets) with talc, sand, polymeric films, or other non-adhesive surfacing materials that remain on the base sheets after installation inhibits the adhesive bonding of self-adhering or conventional cap sheets and other roof system components to the top major surfaces of these base sheets.